In semiconductor devices, such as IC's, LSI's and hybrid IC's, in order to protect semiconductor elements and external leads connected to bonding wires of the semiconductor elements against their environment, resin-sealing is widely employed, using silicone resin, epoxy resin, phenol resin or the like. FIG. 1 shows a cross-section of a conventional semiconductor device sealed with resin, which comprises a semiconductor element 1 mounted on a die frame 2 of, for example, Cu or Fe-Ni material, and Au bonding wires 3 which connect the semiconductor element 1 to external leads 7. The semiconductor element 1, the bonding wires 3 and the external leads 7 are sealed by a sealing resin 6, such as an epoxy resin.
In the above-described conventional resin-sealed semiconductor device, stress may be generated in a heat cycle due to difference in coefficient of linear expansion between the sealing resin 6 and the semiconductor element 1. Such as stress tends to cause problems such as deformation of fine aluminum conductors on the semiconductor element 1, cracking of a passivation coating, peeling off of bonding pads 4, cracking of the sealing resin 6, etc.
FIG. 2 shows a cross-section of a conventional hybrid IC sealed with a liquid silicone potting resin, which comprises a semiconductor elements 1 mounted on a ceramic substrate 9. The semiconductor elements 1 are connected to aluminum conductors or external leads (not shown) printed on the substrate 1 by means of Au bonding wires 3. Then, the semiconductor elements 1, the Au bonding wires 3 and the external leads are sealed with a liquid silicone potting resin 8. This semiconductor device also has problems similar to those of the device of FIG. 1, i.e. deformation of fine aluminum wires on the semiconductor element 1, cracking of a passivation coating, peeling off of bonding pads 4, etc.
Japanese Published Patent Application No. SHO 63-275625 discloses a semiconductor device which uses a sealing epoxy resin modified with silicone rubber to reduce the elasticity of the epoxy resin so that stress generated in the heat cycle may be reduced. Even such a silicone rubber-modified epoxy resin, however, cannot completely prevent stress from being generated during the heat cycle, and, therefore, this technique cannot adapt itself to manufacuring large-size semiconductor elements. In The 38th Netsu-Koka-Sei-Jushi Koen-Toron-Kai Koen-Yoshi-Shu (containing the abstracts of the lectures held on the 38th meeting for lectures and discussions on thermosetting resins), pages 123-126, a technique has been reported, according to which a large amount of inorganic filler is mixed with a sealing resin, whereby the coefficient of linear expansion of the sealing resin decreases, which, in turn, reduces stress generated during the heat cycle. However, with this technique, it is still impossible to match the coefficient of linear expansion of the semiconductor element and that of the sealing resin with each other, and, therefore, it is very difficult to suppress the generation of stress. Furthermore, mixing of a large quantity of inorganic filler to a sealing resin causes the viscosity of the resin to increase so that the moldability of the resin decreases.
Therefore, an object of the present invention is to provide a resin-sealed semiconductor device which is free of the above-described problems, and which has good thermal resistance, good humidity resistance and good thermal shock resistance, so that possibility of deformation of fine aluminum wires, cracking of a passivation film, cracking of sealing resin and the like is greatly reduced.